Oracle chairman Larry Ellison’s billion-dollar holding in the luxury electric-car maker Tesla was revealed in a filing with the Securities and Exchange Commission.Ellison, a long-time friend of Tesla (ticker: TSLA) chief executive officer Elon Musk, joined the electric-car maker’s board in December and has been critical of what he charges is unfair media coverage of the outspoken Musk.

Tesla named Oracle (ORCL) chairman and an executive from Walgreens (WBA) to its board as part of a settlement with regulators who demanded more oversight of the CEO. Musk drew SEC scrutiny in early August when he said in a tweet that he had “funding secured” to take the electric car company private at $420 per share, a claim he later walked back. The SEC accused Musk of securities fraud. The agency accepted the board shuffle and $20 million in penalties to settle the case.In October Ellison said Tesla was his second-largest investment, although he was not more specific at the time.

With a net worth of $51.4 billion, Ellison ranks as the world’s ninth-richest person on the Bloomberg Billionaires Index.Tesla shares are up about 0.9{119d3868ef95c75b95c842798064b27b98a88237d49671f878767e084d0a6a4a} in Tuesday’s premarket after a more than 5{119d3868ef95c75b95c842798064b27b98a88237d49671f878767e084d0a6a4a} jump Monday. The stock is down about 0.4{119d3868ef95c75b95c842798064b27b98a88237d49671f878767e084d0a6a4a} over the last 12 months, according to FactSet. It is up 0.6{119d3868ef95c75b95c842798064b27b98a88237d49671f878767e084d0a6a4a} so far in January.